Implantation of surgical stents into body lumens to support a region of the lumen adjacent a lesion is a well known therapy which is beneficial in a variety of different circumstances. Surgical stents come in a variety of different configurations. Many such surgical stents are generally cylindrical in form and have a first radially collapsed configuration and a second radially expanded configuration. For instance, the patent to Frantzen (U.S. Pat. No. 5,843,175) illustrates a typical such stent.
Known prior art methods for delivery of such stents typically involve radially collapsing the stent onto an inflatable balloon while the balloon is in a deflated configuration having a lesser radial size. The balloon and stent combination are fed along the body lumen with a guide wire or other support structure controlled by the surgeon. The support can also supply a fluid to an interior of the balloon for radial expansion of the balloon. When the balloon and stent combination in their collapsed form have been positioned where desired within the body lumen, the balloon is inflated, causing the balloon to expand radially and for the stent to expand radially. When the stent is expanded to the desired amount, the balloon can then be deflated and removed. The stent remains in place to support the body lumen.
Known prior art balloon and balloon/stent combined delivery systems suffer from deficiencies which this invention addresses. For instance, prior art balloons are not sufficiently flexible to be easily passed into tortuous and tightly curving body lumens, such as many coronary arteries. This lack of balloon flexibility is particularly noticeable when the prior art balloons are inflated and have a tendency to straighten within the body lumen. Such balloon straightening can undesirably damage the body lumen or cause the balloon to migrate out of the position desired for implantation of the stent.
Additionally, prior art balloons have generally not been provided with sections having differing expanded radial sizes. Hence, when stents having a tapering or otherwise variable diameter are to be implanted, balloons have not been available which have variable radial sizes to match such stents.
Accordingly, a need exists for a stent delivery system featuring a flexible balloon and a balloon which can have separate sections of different radial size to maximize the effectiveness of the stent implantation process.